Error when upgrading database to anything higher than 7.5 [Solved]

I'm having major issues upgrading an umbraco solution from version 7.2.2.

When i'm running the database step i'm getting the following error:

The database failed to upgrade. ERROR: The database configuration failed with the following message: Cannot insert duplicate key row in object 'dbo.umbracoNode' with unique index 'IX_umbracoNode_uniqueID'. The duplicate key value is (dfab0389-5001-3e87-8d80-ce45b313e25b).
The statement has been terminated. Please check log file for additional information (can be found in '/App_Data/Logs/UmbracoTraceLog.txt')

The thing is i cannot even find a property in my database with that UniqueID... Anything encountered something similar ?

How are you going about the upgrade? Have you tried making large jumps or have you been going through smaller increments?

If upgrading from 7.2.2, I would advise upgrading in fairly small increments and making sure you read the version specific upgrades notes. Some of the early upgrades can be pretty problematic if you take too big a jump.

So my upgrade process would probably be:

Upgrade to the latest 7.2.* version

Upgrade to 7.3.0

Upgrade to 7.3.* latest

Upgrade to 7.4.* latest

Upgrade to 7.5.* latest
etc.

After about 7.4, I've found the upgrades have become a lot smoother but the version-specific notes are still very important, particularly the 7.6 notes.

Yeah i also came across that thread before posting here. Should have mentioned that obviously. Anyway i tried both deleting that index, and unless im at a fault then my user should be set to DBO.

just to be sure: the default schema is configured by (using MS SQL Server management studio) rightclicking my user. clicking properties. selecting user mapping and then setting the database role as db_owner on the user. I altroed pressing the "Default schema" box, and then manually typing DBO for object names. but i think those two solutions are equivalent....

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